In Senate races, Democrat leads Republican in Arizona, North Carolina a dead heat - Reuters/Ipsos poll

FILE PHOTO: Democratic Senate candidate Mark Kelly encourages supporters and volunteers to continue reaching voters in the final days of the campaign during the kick off volunteers launch in Tucson Arizona U.S., October 27, 2020. REUTERS/Edgard Garrido/File Photo

WASHINGTON (Reuters) - Democratic U.S. Senate candidate Mark Kelly held a big lead over Arizona Republican incumbent Martha McSally on the eve of the election while Republican and Democrat vying for Senate seat in North Carolina were running neck-and-neck, a Reuters/Ipsos poll showed on Monday.

The outcome of about 14 of 35 U.S. Senate races is anyone's guess in Tuesday's election, 12 with vulnerable Republican incumbents and two with vulnerable Democrats. To have a majority in the Senate, Democrats need to pick up three seats if they also win the White House, which gives the vice president a tie-breaking vote, and four if not.